P0017
- Powertrain
- Generic (SAE)
- Emissions
Get it looked at now
A crank-to-cam correlation fault means the mechanical timing may already have moved. On an interference engine, a chain that slips further can bring pistons and valves into contact and destroy the engine. The vehicle may also stall or fail to start without warning, and a stall at speed costs power steering assist and, once the vacuum reservoir is used up, power brake assist. Even when the cause turns out to be a sensor, the possibility of a slipped chain is serious enough to justify caution until it is ruled out.
- Safe to drive
- Do not drive it. Have it towed rather than driven to the shop, especially if it rattles at start-up, runs rough, or stalls. A slipping chain on an interference engine bends valves, and every additional start is another chance for it to jump. If it does stall while moving, expect heavy steering and a hard brake pedal — the brakes still work but need far more effort.
Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor B)
The computer compared the crankshaft signal against the bank 1 B camshaft signal and the two do not line up the way they should. That points at the mechanical timing between crank and cam, or at the sensors and reluctor wheels that read them.
The module knows the exact angular relationship that should exist between the crankshaft reference signal and each camshaft position signal. It measures the phase between them across a number of engine revolutions and compares against a calibrated window. P0017 sets when the bank 1 B camshaft, normally the exhaust cam on a dual-overhead-cam engine, is outside that window. Unlike the phaser performance codes, this is not about whether the cam responded to a command; it is about whether the cam is physically where the crankshaft says it should be.
How the car detected itThe correlation test runs early, often within a few seconds of a start, because the module needs a valid crank-to-cam relationship to sequence fuel and spark. It typically requires stable engine speed rather than any particular temperature or load. A phaser that fails to lock at its parked position during shutdown will produce a correlation fault only at the next start, which is why this code often appears together with a brief start-up rattle.
A trouble code records what a control module measured. It does not identify which part failed. Test before replacing anything.
- Safe to drive
- Do not drive it. Have it towed rather than driven to the shop, especially if it rattles at start-up, runs rough, or stalls. A slipping chain on an interference engine bends valves, and every additional start is another chance for it to jump. If it does stall while moving, expect heavy steering and a hard brake pedal — the brakes still work but need far more effort.
- Urgency
- Get it looked at now
- Will it pass emissions
- No
- If ignored
- Hard starting, no-start, stalling, and reduced power. If a chain, guide, or tensioner is worn, continued running lets the chain slip further, and on an interference engine that means valve-to-piston contact, bent valves, and possibly a damaged head or piston. The cost difference between fixing the chain now and rebuilding the engine later is the whole argument for stopping.
- Check engine light
- Solid
- Clearing the light
- A completed drive cycle is normally required before the monitor re-runs and the light can clear.
- Power loss especially in mid-rpm range
- Possible rough idle or stalling
- Increased fuel consumption
Many vehicles show no symptom at all beyond the warning light. The absence of a symptom does not mean the fault is not real.
These are the causes this code can have. For the order to work through them in, see what to check first.
| # | Cause | How often | Component |
|---|---|---|---|
| 1 | Timing chain stretched | Very common | — |
| 2 | Exhaust cam phaser failed | Common | — |
Ordering reflects how often each cause is responsible in general, not a probability for your vehicle. Confirm by testing.
In order. Each of these is cheaper or faster than what follows it, and each one can make the rest unnecessary.
Any rattle for the first second or two after a cold start
A brief start-up rattle is the classic signature of a worn chain tensioner or guide, or a phaser that is not locking. It is free to listen for and it reframes the entire diagnosis before anything is removed.
Engine oil level, condition, and pressure
Chain tensioners and phaser lock pins are oil-pressure operated. Low or degraded oil produces correlation faults on a mechanically sound engine, and it is the cheapest thing to correct.
Every other stored code and the order they set
Companion VVT performance codes, circuit codes, misfire codes, or other correlation codes tell you whether this is a single-cam problem or a whole-chain problem, and that determines the size of the repair.
Recent timing chain, phaser, camshaft, or cylinder head work
A chain installed one tooth out or a cam sprocket bolt not torqued correctly is a leading cause of P0017 after service, and the fix is to redo the job rather than to buy new parts.
The camshaft and crankshaft sensor connectors and mounting
A loose sensor, a damaged connector, or debris on the sensor tip can corrupt the signal and set a correlation code with the mechanical timing perfectly intact. It is a five-minute check before a multi-thousand-dollar teardown.
Record all codes and freeze frame before clearing anything
Tools Scan tool
Note rpm, temperature, run time, and load at the fault. Capture whether the code sets on every start or only intermittently. Companion codes are critical here and must be listed in the order they set.
ExpectedA complete code list in the order the codes set, with the recorded conditions at the fault, captured before anything is cleared
Check oil level, condition, and measure hot oil pressure with a mechanical gauge
Tools Mechanical oil pressure gauge and adapter
The dash light only warns of catastrophic loss. Measure real pressure at idle and raised rpm at operating temperature. Port location and specification are engine-specific. Inadequate pressure starves the chain tensioner and the phaser lock pin and can cause this code without any part being worn out.
ExpectedOil full and clean, and measured pressure meeting the engine's specified figure hot at both idle and raised rpm
Listen carefully at a cold start
Tools Stethoscope or careful listening
A rattle that lasts a second or two and then quietens is chain slack that the tensioner eventually takes up. A continuous rattle is worse. A metallic knock is a different problem entirely and means stop immediately.
ExpectedClean, quiet start with no rattle
Scope the crankshaft and camshaft signals together
Tools Two-channel lab scope, known-good reference waveform
Capture both on a two-channel scope and examine their phase relationship and signal quality. This separates a genuine timing shift from a corrupted or dropping-out sensor signal. The correct waveform relationship is engine-specific and must be compared against known-good reference data for that engine.
ExpectedA crank-to-cam phase relationship matching known-good reference data for that engine, with clean signals and no dropouts on either channel
Inspect sensors, mounting, and reluctor wheels
Tools Hand tools, inspection light, magnet
Remove the camshaft and crankshaft sensors and check for metal debris on the tips, damage, and correct seating. Check for a cracked, loose, or slipped reluctor wheel and a loose cam sprocket or its retaining bolt. Metal on a sensor tip is itself evidence of internal wear.
ExpectedClean sensor tips, tight mounting, undamaged reluctor wheels
Verify mechanical timing directly against the manufacturer's reference
Tools Hand tools, service data, manufacturer timing tools
Bring the engine to the specified timing reference position and compare cam and crank marks, or measure tensioner extension or chain slack through whatever access provision the engine has. Every part of this procedure varies by engine and must come from service data. This is the step that definitively separates sensor faults from a moved chain.
ExpectedCam and crank marks aligned at the manufacturer's reference position, with tensioner extension or chain slack inside the service-data limit
Check for manufacturer service bulletins for that engine
Tools Service information subscription
Several engine families have known chain, guide, tensioner, or phaser issues with published procedures and updated parts. Checking bulletins before a teardown can save both parts and repeat work. Which engines and which bulletins vary entirely by make and model.
ExpectedA documented answer either way — an applicable bulletin for this engine and build range, or confirmation that none applies
Assess valve and cylinder condition after mechanical timing is restored
Tools Compression tester or leak-down tester
On an interference engine whose timing was found out by one or more teeth, a compression or leak-down test taken while the timing is still wrong reads low on every cylinder and proves nothing — it cannot separate bent valves from the mistiming itself, and it risks condemning a good cylinder head. Restore correct timing at the manufacturer's reference position first, then test. That is the point at which bent valves show up as a single cylinder or a pair reading low against the rest.
ExpectedWith timing corrected, even compression across all cylinders within the engine's specified variation. One cylinder or a pair low against the others points at valve damage.
| Repair | Only after you confirm | Typical cost | Who |
|---|---|---|---|
| Oil and filter change with the correct specified viscosity, plus correction of low oil level | Oil found low, sludged, or the wrong viscosity, with measured pressure restored and no correlation error after a drive cycle | $60–$200 | DIY |
| Replace the camshaft or crankshaft position sensor | Scope capture shows a corrupted or dropping signal from that sensor while the mechanical timing is verified correct at the reference position | $150–$450 | DIY |
| Repair sensor wiring, connector, or a damaged reluctor wheel | Physical damage found, or a signal dropout that follows harness movement during a scoped wiggle test | $150–$800 | DIY |
| Correct mechanical timing that was assembled incorrectly, or retorque a loose cam sprocket | Direct inspection at the timing reference position showing marks out of alignment or a loose sprocket fastener | $500–$1,800 | Shop |
| Replace the timing chain, guides, tensioner, and phasers as a set | Measured chain slack or tensioner extension beyond specification, or timing marks confirmed out at the reference position | $1,200–$4,500 | Shop |
| Repair valve or piston damage caused by a slipped chain | Compression or leak-down test failing on specific cylinders after correct mechanical timing has been restored on an interference engine — a test taken before timing is corrected reads low everywhere and cannot confirm this | $2,500–$8,000 | Shop |
Chain jobs vary more than almost any other repair. A longitudinal four-cylinder with a front-mounted chain sits at the low end; a transverse V6 with rear-bank access, or an engine that must come out, sits well above it. Get the diagnosis right before authorizing, because the difference between a sensor and a chain here is thousands of dollars. Ranges are US independent-shop, parts plus labor.
- Replacing camshaft and crankshaft sensors repeatedly because they are cheap, while a stretched chain quietly gets worse.
- Compression testing an interference engine while the cam timing is still known to be out. Every cylinder reads low, the result proves nothing, and it has condemned good cylinder heads.
- Replacing the chain but reusing the original guides and tensioner. The guides are the part that usually wears, and the code comes back.
- Missing a loose or backed-out camshaft sprocket bolt, which produces this code and can destroy the engine if it lets go.
- Skipping the oil pressure measurement. Tensioners and phaser lock pins are hydraulic, and low pressure causes correlation faults on intact hardware.
- Clearing the code and continuing to drive an interference engine while deciding what to do. That is how a chain job becomes an engine job.
- Installing phasers onto a worn chain, or a chain onto worn phasers, when the labor to open the cover is the same either way.
- Definition
- Generic code set (SAE J2012 / ISO 15031-6) via the OBDexopen database, dedicated to the public domain under CC0-1.0.
- Diagnostic guidance
- Written and reviewed in-house. See our editorial policy.
- Review status
- Reviewed
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